1. Field of the Invention
The present invention generally relates to electro-optical cells (EO-cells) which comprise two transparent electrodes and a layer of liquid crystals interposed between said electrodes. The invention more specifically relates to an optical filter for use in a protective welding lens assembly in a welder's helmet or visor, said filter being made up of EO-cells of the above-mentioned type and having a filter sheet disposed in the ray path for eliminating residual light.
2. Description of the Prior Art
Electro-optical cells using liquid crystals have been suggested for and also come into practical use in protective welding lens assemblies. This has conferred the advantage that the visor of the welder's helmet need not be raised and lowered between the different welding operations.
The electro-optical filters hitherto suggested and used do however not meet all the demands which should be placed on e.g. a protective welding lens assembly.